Treatment Of Textile Fabrics

ABSTRACT

Textile fabrics comprising not less than 70% by weight of cellulose are treated with solutions of one or more silicon compounds in liquid ammonia. Cellulose molecules are crosslinked by the treatment, producing good wrinkle resistance and good water retention capacity.

This invention relates to a process for treating a textile fabric whichcomprises applying a certain silicon compound or a mixture of siliconcompounds to the fabric and subsequently drying the fabric.

It is known to treat textile fabrics comprising cellulosic fibers withliquid ammonia. This is typically done in the case of textile fabricswhich are to be cured in the moist state.

It is likewise known to treat cellulosic fabrics with cellulosecrosslinkers in order that the wrinkling characteristics of theready-produced articles may be beneficially influenced. For this, thefabrics are typically processed on a pad-mangle in the course of afinishing process. The padding liquor is normally an aqueous solution ordispersion. This solution or dispersion will comprise one or morecellulose crosslinkers and also, if appropriate, further desiredingredients such as softeners for example.

Known cellulose crosslinkers include N-methylol compounds. These doindeed lead to good crosslinking results, but may be consideredproblematical because they include formaldehyde as a by-product orrelease by-produced formaldehyde at elevated temperature or in thecourse of storage. Prior artisans have searched for alternativecrosslinkers which neither contain formaldehyde nor release it in thecourse of processing. They found that silanes can also be used tocrosslink cellulosic fibers.

Processes utilizing silane cellulose crosslinkers are known. Forinstance U.S. Pat. No. 3,055,774, EP-A 563 961 and EP-A 401 668 describethe treatment of cellulose or cellulose derivatives with functionalsilanes. The silane is used in the form of an aqueous composition in allof these processes.

It has been determined that the crosslinking of cellulosic articles withaqueous systems comprising silanes does not always lead to optimalcrosslinking results with regard to, for example, crease recovery, waterretention capacity and so on. Moreover, certain reactive silanes cannoteven be used to crosslink via aqueous systems since they will react withwater or their cellulose reactivity is less than optimal in aqueoussystems. These kinds of reactive silanes include, for example, silanesin which alkoxy groups are attached to the silicon atom. Specificallythese silanes will be desirable for use as crosslinkers because of theircellulose reactivity.

The present invention has for its object to provide a process foreffective crosslinking of textile fabrics having an appreciablecellulosic fiber content. The process shall further be able to employ ascrosslinkers even those silicon compounds which are instable or lessthan optimally reactive in aqueous systems.

We have found that this object is achieved by a process for treating atextile fabric having a cellulosic fiber content in the range from 70%to 100% by weight with a solution in liquid ammonia of a siliconcompound or of a mixture of silicon compounds, which process comprisesapplying this solution to the textile fabric and then drying the fabric,

wherein at least one of the silicon compounds used conforms to one ofthe formulae (I) to (IV)

where

all R radicals are independently hydrogen or an alkyl radical having 1to 4 carbon atoms,

all R¹ radicals are independently an alkyl radical having 1 to 18 carbonatoms or phenyl,

the R² radical is a radical of the formula (V) or of the formula (VI)

where Ep is the univalent radical derived from ethylene oxide or is anepoxycyclohexyl radical, preferably 3,4-epoxy-1-cyclohexyl,

n is from 2 to 4,

a is from 1 to 3,

b is 3−a,

c is from 1 to 4, preferably 2,

d is 1 to 5,

e is from 1 to 4, preferably 1 or 3,

t is from 1 to 3,

y is from 1 to 3, preferably 1, and

t+y is from 2 to 4.

The process of the present invention is for treating textile fabricshaving a cellulosic fiber content in the range from 70% to 100% byweight. The textile fabrics contemplated include wovens, knits andnonwovens. Wovens are preferred.

The cellulosic fiber content of the textile fabrics ranges from 70% to100% by weight. When the cellulosic fiber content is less than 100%, theremainder may consist of synthetic fibers such as polyester or polyamidefor example. Cellulosic fibers may consist of natural cellulose such ascotton for example or else of regenerated cellulose.

Textile fabrics treated by the process according to the presentinvention can be further processed into garments for example.

The process of the present invention has a number of advantages:

a) high crosslinking effectivity, frequently higher than crosslinkingwith the same silicon compounds in an aqueous medium.

b) can utilize even silanes which are highly cellulose reactive butwhich cannot be employed in the form of aqueous systems since they lackstability or reactivity in aqueous systems.

c) where the textile fabric is in any case to be treated with liquidammonia it is frequently possible to save a processing stage, namely aseparate operation to apply a cellulose crosslinker, since thecrosslinker has already been applied (in the form of a solution inliquid ammonia).

On the other hand, it will be understood that a separate finishingoperation may be carried out nonetheless, for example when furtherproducts in the form of aqueous solutions or dispersions are to beapplied after the fabric has passed through the process of the presentinvention. Such products may include softeners, fluoropolymers or flameretardants, well known to those skilled in the textile-finishing arts.

d) a customary moist cure can be omitted after the process of thepresent invention has been carried out. It is thus preferable not tocarry out a moist cure after the process of the present invention. Onthe contrary, very good crosslinking results are already provided by thepresent invention's process after drying with or without curing. Thiscan be ascertained by means of the hereinbelow described determinationof the wrinkle properties via determination of the wet crease angle.

e) the process of the present invention can be carried out without usingproducts which contain formaldehyde or release it at elevatedtemperature.

In the process of the present invention, the identified textile fabricsare treated with a solution in liquid ammonia of a silicon compound ofthe hereinbelow described type. A mixture of silicon compounds can beused in place of a single silicon compound. At least one of the siliconcompounds used shall conform to one of the hereinbelow illustratedformulae (I) to (IV). Preferably, all silicon compounds used fall underone of these formulae; that is, preferably no silicon compound ispresent which does not conform to any of the formulae (I) to (IV), butamino-functional polysiloxanes or other softeners can also be present inthe solution in liquid ammonia. However, all employed silicon compoundsand other softeners have to be readily soluble in liquid ammonia.

The applying of the ammoniacal solution to the textile fabric can beeffected by methods known in the textile industry. Application by meansof a bath, for example on a pad-mangle where the fabric is dipped into asolution of the desired silicon compound in liquid ammonia, isparticularly suitable. The residence time of the textile fabric in theammoniacal solution will normally be about 20 seconds to 20 minutes, butit can also be longer. This is followed by squeezing off in a knownmanner.

The solution of the defined silicon compound or of the mixture ofsilicon compounds at the time of application to the fabric is preferablyat a temperature in the range from −60° C. to −40° C. This temperaturerange shall apply irrespectively of which application method is used.The amount of silicon compound in the ammonia solution is normally about0.01 to 3 parts by weight, and preferably 0.1 to 0.7 part by weight, per100 parts by weight of ammonia. These numerical statements relate to thetotal amount of all silicon compounds used which fall under one of theformulae (I) to (IV).

It is particularly advantageous and therefore preferable when thesolution of the silicon compound or compounds in liquid ammonia furthercomprises a catalyst. Suitable catalysts provide an increased degree ofcrosslinking and hence better effects with regard to the creaseresistance of ready-produced textiles and/or its durability. Stericallyhindered amines such as for example diazabicyclo[2.2.2]octane (DABCO) or4-dimethylaminopyridine (4-DMAP) are particularly suitable for use ascatalysts. The amount of catalyst added is preferably in the range from1.0% to 3% by weight, based on the total amount of silicon compounds ofthe formulae (I) to (IV) present in the ammoniacal solution.

The textile fabric has to be dried after the ammoniacal solution hasbeen applied to it. Known drying apparatuses can be used. Drying isnormally done at a temperature in the range from 60° C. to 180° C. andpreferably from 80° C. to 150° C., and is carried on until ammonia,water and any alcohol formed have been removed. This normally requires adrying time of about 5 to 30 minutes. Water or alcohol are formed in thecrosslinking reaction with OH groups on the cellulose when siliconcompounds are used in which OH or OR groups are attached to siliconatoms.

It is frequently of advantage to Sanforize the textile fabric before itis dried. Sanforizing is a process of controlled compressive shrinkageapplied to textile material, described for example in K. Peter, H. K.Rouette, Grundlagen der Textilveredelung, 13th edition, dfv DeutscherFachverlag 1989, Frankfurt/Main, in particular pages 718 to 721.

After the textile fabric has been dried it may, if desired, beremoistened with water.

In one preferred embodiment of the process according to the presentinvention the textile fabric is cured after it has been dried, inparticular when the drying temperature is below 130° C. Curing in thissense is a treatment at elevated temperature, for example in the rangefrom 130° C. to 180° C. and preferably in the range from 140° C. to 170°C., for a period from 2 to 10 minutes. Curing can be used to increasethe number of bonds which form between the cellulose and the reactivesilicon compounds.

At least one of the silicon compounds used for the process of thepresent invention shall conform to one of the formulae (I) to (IV)

In these formulae

-   -   all the R radicals are independently hydrogen or an alkyl        radical having 1 to 18 carbon atoms. Preferably, all the R        radicals present are each an alkyl radical having 1 to 4 carbon        atoms. This alkyl radical may be linear or branched. More        preferably, all the R radicals are independently a methyl or        ethyl group.    -   all the R′ radicals are independently an alkyl radical having 1        to 18 carbon atoms or unsubstituted phenyl. Preferably, all the        R′ radicals are each either methyl or ethyl.    -   the R² radical is a radical of the formula (V) or of the formula        (VI)

-   -   Ep is the univalent radical derived from ethylene oxide, i.e.,        the radical formed on removing a hydrogen atom from the formula        for ethylene oxide (oxirane), or an epoxycyclohexyl radical,        preferably 3,4-epoxy-1-cyclohexyl

n is from 2 to 4,

a is from 1 to 3,

b=3−a,

c is from 1 to 4, preferably 2,

d is from 1 to 5,

e is from 1 to 4, preferably 1 or 3,

t is from 1 to 3,

y is from 1 to 3, preferably 1, and

t+y is from 2 to 4.

It has been determined that optimal crease resistance results in manycases when c=2.

All these silicon compounds contain 2 or more reactive groups capable ofreacting with the OH groups of cellulose, if necessary at elevatedtemperature. The result of this reaction is a crosswise linking togetherof cellulose chains which improves crease resistance.

Silicon compounds or silanes of the formulae (I) to (IV) and theirpreparation are known from the prior art, for example from thereferences cited at the beginning and from EP-A 1 199 339, or arepreparable by processes known to one skilled in the art, for example byreaction of halosilanes with alcohols. Furthermore, silicon compounds ofthe formulae (I) to (IV) are commercially available, for example fromWacker, Germany.

The process of the present invention provides textile fabrics which haveexcellent properties with regard to creasing/wrinkling and waterretention capacity, these properties being very durable to storage andlaundering operations.

An instrument to determine the crease recovery angle wet (also known aswet crease angle) is described in Melliand Textilberichte, Vol. 39, No.5, pages 552-554. This instrument can be used to determine thecreasing/wrinkling characteristics of textile fabrics. The values ofcrease recovery angle wet which are reported hereinbelow in Examples 1a)to 1d) are based on determinations in accordance with this Melliandreference.

The samples were prepared as follows for this determination:

Woven fabric samples 2 cm×1 cm in size were placed in an aqueoussolution containing 1 g/l of wetting agent (sodium salt of analkylnaphthalenesulfonate). After 5 minutes, the samples were removed,laid on a plastics rail, folded and loaded with 500 g weight for 3minutes. The weight was then removed for 3 minutes before the creaserecovery angle was measured.

The invention will now be illustrated by examples.

EXAMPLES 1a) to 1d)

25 ml of ammonia are condensed in an apparatus at −40° C. or −60° C.,0.1 ml of alkoxysilane is added, and the contents of the apparatus aremixed until homogeneous. The identity of the alkoxysilane was varied invarious experiments and is stated in tables 1 to 4. A hindered aminecatalyst was added in some experiments. A woven fabric is then added,removed again after a defined period and warmed to room temperature.After the ammonia has evaporated off, the fabric is dried in a dryingcabinet with or without curing. The woven fabric used was 100% cotton inall Examples 1a) to 1d).

The experimental conditions of Examples 1a) to 1d) are tabulated below.A different silicon compound (alkoxysilane) was used in each of these 4examples. Where a catalyst was used as well, its amount was 2.5% byweight, based on the silicon compound, in each case.

EXAMPLE 1a)

TABLE 1 0.1 ml of γ-glycidoxypropyltriethoxysilane in 25 ml of ammonniaResidence Ammonia Drying (T) and Crease time in temperature curing (K)recovery angle ammonia Catalyst [° C.] conditions wet [°] 30 s — −40 10min 110° C. + 71 5 min 150° C. (T + K) 5 min DABCO −40 10 min 110° C. 75(T) 5 min DABCO −40 10 min 110° C. + 82 5 min 150° C. (T + K)

EXAMPLE 1b)

TABLE 2 0.1 ml of 1,2-bis(methoxydimethylsilyl)ethane in 25 ml ofammonia Crease Residence Ammonia Drying (T) recovery time in temperatureand curing (K) angle ammonia Catalyst [° C.] conditions wet [°] 30 s —−40 10 min 110° C. (T) 71 30 s — −40 10 min 110° C. + 80 5 min 150° C.(T + K) 1 min — −40 10 min 110° C. (T) 73 1 min — −40 10 min 110° C. +84 5 min 150° C. (T + K) 5 min DABCO −60 10 min 110° C. (T) 75 5 minDABCO −60 10 min 110° C. + 82 5 min 150° C. (T + K) 5 min DABCO −40 10min 110° C. (T) 72 5 min DABCO −40 10 min 110° C. + 80 5 min 150° C.(T + K)

EXAMPLE 1c)

TABLE 3 0.1 ml of γ-glycidoxypropylmethyldiethoxysilane in 25 ml ofammonia Residence Crease time in Ammonia Drying (T) recovery ammoniatemperature and curing (K) angle [min] Catalyst [° C.] conditions wet[°] 5 DABCO −40 10 min 110° C. + 76 5 min 150° C. (T + K)

EXAMPLE 1d)

TABLE 4 0.1 ml of triethoxy(2,4,4-trimethylpentyl)silane in 25 ml ofammonia Residence Ammonia Crease time in temperature Drying conditionsrecovery angle ammonia [° C.] (T) wet [°] 10 s −40 10 min 110° C. (T) 72 1 min −40 10 min 110° C. (T) 78 Higher “crease recovery angles wet”values mean improved crease recovery performance.

1. A process for treating a textile fabric having a cellulosic fibercontent in the range from 70% to 100% by weight with a solution inliquid ammonia of a silicon compound or a mixture of silicon compounds,which process comprises applying this solution to the textile fabric andthen drying the fabric, wherein at least one of the silicon compoundsused conforms to one of the formulae (I) to (IV)(RO)_(n)Si(R¹)_(4-n)  (I)(RO)_(t)Si(R¹)_(4-t-y)(R²)_(y)  (II)(R¹)_(b)(RO)_(a)Si—(CH₂)_(c)—Si(OR)_(a)(R¹)_(d)  (III) and(RO)_(a)(R¹)_(b)—Si—O[Si(R¹)₂]_(d)—O—Si(R¹)_(b)(OR)_(a)  (IV) where allR radicals are independently hydrogen or an alkyl radical having 1 to 4carbon atoms, all R¹ radicals are independently an alkyl radical having1 to 18 carbon atoms or phenyl, the R² radical is a radical of theformula (V) or of the formula (VI)—(CH₂)_(e)-Ep  (V)—(CH₂)_(e)—O—CH₂-Ep  (VI) where Ep is a univalent radical derived fromethylene oxide or is an epoxycyclohexyl radical, n is from 2 to 4, a isfrom 1 to 3, b is 3−a, c is from 1 to 4, d is from 1 to 5, e is from 1to 4, t is from 1 to 3, y is from 1 to 3, t+y is from 2 to
 4. 2. Aprocess according to claim 1, characterized in that a curing operationis carried out subsequent to the drying step.
 3. A process according toclaim 1, characterized in that the solution in the liquid ammoniacomprises from 0.1 to 0.7 part by weight of silicon compound orcompounds of the formulae (I) to (IV) per 100 parts by weight ofammonia.
 4. A process according to claim 1, characterized in that theapplying of the solution to the textile fabric is effected by a paddingoperation and at a temperature for the solution in the range from −40 to−60° C.
 5. A process according to claim 1 4, characterized in that thetextile fabric is Sanforized before being dried.
 6. A process accordingto claim 1, characterized in that the solution in liquid ammonia furthercomprises a catalyst in an amount from 1% to 3% by weight, based on thetotal amount of silicon compounds of the formulae (I) to (IV) present inthe solution.
 7. A process according to claim 6, characterized in thatthe catalyst is a sterically hindered amine or a mixture of stericallyhindered amines.
 8. A process according to claim 7, wherein the catalystis diazabicyclo[2,2,2]octane or 4-dimethylaminophydine.